The Chinese giant salamander (Andrias davidianus) is the largest salamander and the largest amphibian in the world.Andrias davidianus -Amphibiaweb It is fully aquatic, and is endemic to rocky mountain streams and lakes in the Yangtze river basin of central China. It has also been introduced to Kyoto Prefecture in Japan, and possibly to Taiwan. It is considered critically endangered in the wild due to habitat loss, pollution, and overcollection, as it is considered a delicacy and used in traditional Chinese medicine. On farms in central China, it is extensively farmed and sometimes bred, although many of the salamanders on the farms are caught in the wild. It has been listed as one of the top-10 "focal species" in 2008 by the Evolutionarily Distinct and Globally Endangered project.
The Chinese giant salamander is considered to be a "living fossil". Although protected under Chinese law and CITES Appendix I, the wild population has declined by more than an estimated 80% since the 1950s. Although traditionally recognized as one of two living species of Andrias salamander in Asia, the other being the Japanese giant salamander, evidence indicates that the Chinese giant salamander may be composed of at least five cryptic species, further compounding each individual species' endangerment.
Taxonomy
The correct scientific name of this species has been argued to be Andrias scheuchzeri (in which case Andrias davidianus would be a junior synonym) – a name otherwise restricted to an extinct species described from Swiss fossils.Amphibian Species of the World 5.2. Genus Andrias. Retrieved 2008-12-28. It has also been given the moniker of "living fossil" for being part of the family Cryptobranchidae which dates back 170 million years. It is one of only five to six known extant species of the family, the others being the slightly smaller, but otherwise very similar Japanese giant salamander (Andrias japonicus), the slightly larger South China giant salamander (A. sligoi), the Jiangxi giant salamander (Andrias jiangxiensis), the Qimen giant salamander (Andrias cheni), and the far smaller North American hellbender (Cryptobranchus alleganiensis).
A 2018 study of mitochondrial DNA revealed that there are five wild clades of the Chinese giant salamander, as well as two only known from captives (their possible wild range was previously unknown). They diverged from each other 4.71–10.25 million years ago and should possibly be recognized as cryptic species. Despite this deep divergence, they can hybridize among each other, and also with the Japanese giant salamander. One of these clades was identified in 2019 as Andrias sligoi, a species described in 1924 by Edward George Boulenger and later synonymized with A. davidianus, with the study supporting its revival as a distinct taxon. Another then-undescribed species was also identified that formerly inhabited rivers originating from the Huangshan mountains in eastern China; this was described as Andrias cheni in 2023. In 2022, one of the captive-only clades was described as Andrias jiangxiensis, and was found to have maintained genetically pure wild populations in Jiangxi Province, in contrast to most of the other clades.
Description
It has a large head, small eyes and dark wrinkly skin. Its flat, broad head has a wide mouth, round, lidless eyes, and a line of paired tubercles that run around its head and throat. Its color is typically dark brown with a mottled or speckled pattern, but it can also be other brownish tones, dark reddish, or black. Albinos, which are white or orange, have been recorded.Sparreboom, M.; Wu, Y. (2014). "Andrias davidianus (Blanchard, 1871)". Salamanders of China. Retrieved 23 February 2016. All species of giant salamanders produce a sticky, white skin secretion that repels predators.
The average adult salamander weighs and is in length.Wood, The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc. (1983), It can reach up to in weight and in length, making it the second-largest amphibian species, after the South China giant salamander (Andrias sligoi). The longest recently documented Chinese giant salamander, kept at a farm in Zhangjiajie, was in 2007. At , both this individual, and a long, individual found in a remote cave in Chongqing in December 2015, surpassed the species' typically reported maximum weight.
The giant salamander is known to vocalize, making barking, whining, hissing, or crying sounds. Some of these vocalizations bear a striking resemblance to the crying of a young human child, and as such, it is known in the Chinese language as the "infant fish" ( - Wáwáyú/ ní).
Behavior
Diet
The Chinese giant salamander has been recorded feeding on insects, millipedes, horsehair worms, amphibians (both frogs and salamanders), freshwater crabs, shrimp, fish (such as Saurogobio and Cobitis ), and Asiatic water shrew. Presumably ingested by mistake, plant material and gravel have also been found in their stomachs. Cannibalism is frequent; in a study of 79 specimens from the Qinling–Dabashan range, the stomach content of five included remains of other Chinese giant salamanders and this made up 28% of the combined weight of all food items in the study. The most frequent items in the same study were freshwater crabs (found in 19 specimens), which made up 23% of the combined weight of all food items.
It has very poor eyesight, so it depends on special sensory nodes that run in a line on the body from head to tail. It is capable of sensing the slightest vibrations around it with the help of these nodes. Based on a captive study, most activity is from the earlier evening to the early night. Most individuals stop feeding at water temperatures above and feeding ceases almost entirely at . Temperatures of are lethal to Chinese giant salamanders.
Adult Chinese giant salamanders and maturing Chinese giant salamanders with nonexistent or shrinking gill slits have developed a system for bidirectional flow suction feeding under water. They start by moving to their prey very slowly, then once close enough to them the Chinese giant salamander abruptly gapes its mouth open. The gaping motion of their mouth causes a great increase in the velocity of the water straight ahead of them compared to water coming in from the sides of their mouth. This is possible because of their large, wide, and flat upper and lower jaws. This process causes the prey to shoot back into their mouths as well as a copious amount of water. They then close their mouths, but leave a small gap between their upper and lower lips so that the captured water can escape.
The Chinese giant salamander catches its prey on land with an asymmetrical bite, in such a way that the force created by their jaws will be maximized in the anterior region where their prey is located. After capture they use their bite to subdue and kill their prey, both on land and in water. They are missing a bone which usually lies along the upper cheek region of most salamanders, which gives them a much stronger bite force. The bite force of the adult Chinese giant salamander is much stronger than the bite force of the maturing Chinese giant salamander due to differences in cranial structure.
Chinese giant salamanders esophaguses are made up of four different layers, one of which being a strong muscular tissue used to help move food through to the stomach. The outer most layer has ciliated cells that move mucous from mucous glands over the surface of the esophagus to lubricate it and reduce friction from large foods such as whole crabs. The ciliated structure and flexibility of the Chinese giant salamander's esophagus is hypothesized to be the reason why it is capable of swallowing such large foods.
Chinese giant salamanders are also capable of fasting for several years if they need to. This is possible because of their metabolic reserves as well as their liver, which is capable of up regulating and down regulating certain proteins according to how long they have been fasting for.
Breeding and lifecycle
Both sexes maintain a territory, averaging for males and for females. The reproductive cycle is initiated when the water temperature reaches and mating occurs between July and September. The female lays 400–500 eggs in an underwater breeding cavity, which is guarded by the male until the eggs hatch after 50–60 days. They have a variety of different courtship displays including knocking bellies, leaning side-to-side, riding, mouth-to-mouth posturing, chasing, rolling over, inviting, and cohabiting. When laid, the eggs measure in diameter, but they increase to about double that size by absorbing water. When hatching, the larvae are about long and external gills remain until a length of about at an age of 3 years. The external gills start to slowly decrease in size around 9 to 16 months, the rate of this phenomenon occurs in relation to the rate of dissolved oxygen, breeding density, water temperatures, and individual differences. Maturity is reached at an age of 5 to 6 years and a length of . The maximum age reached by Chinese giant salamanders is unknown, but it is at least 60 years based on captive individuals. Undocumented claims have been made of 200-year-old Chinese giant salamanders, but these are considered unreliable.
Distribution and habitat The Chinese giant salamander species complex comprises five clades, with multiple possibly worthy of species recognition. Their native ranges differ, but release of Chinese giant salamanders from captivity has complicated this picture. They were widespread in central, south-western, and southern China, although their range is now highly fragmented. Their range spans the area from Qinghai east to Jiangsu and south to Sichuan, Guangxi, and Guangdong; notably in the basins of the Yangtze, Yellow, and Pearl Rivers. One clade is from the Pearl River basin (at least in Guangxi), two from the Yellow River basin, one from the Yangtze River basin (at least in Chongqing and Guizhou), and the final from the Qiantang River (at least in Anhui). Two additional clades were only known from captivity (their wild range is unknown) and no samples are available for the population in the Tibetan Plateau. A 2019 study has identified that the Yangtze River clade comprises the "true" A. davidianus, the Pearl River clade comprises A. sligoi, and the Qiantang clade comprises the Huangshan Mountains species (described as A. cheni in 2023). A 2022 study identified one of the two clades known only from captivity as A. jiangxiensis, found in the wild only in Jiangxi Province.
Finds in Taiwan may be the result of introduction, though their exact taxonomic identity is unknown. Chinese giant salamanders have been introduced to the Kyoto Prefecture in Japan where they present a threat to the native Japanese giant salamander, as the two hybridize. A 2024 genetic study confirmed that in spite of the recent taxonomic changes within the genus, the Chinese Andrias species introduced to Japan and hybridizing with A. japonicus is the "true" A. davidianus (the Yangtze River clade, or lineage B), although at least one genetically pure individual of the captive-only lineage U1 was also detected in the wild. The Chinese giant salamander is entirely aquatic and lives in rocky hill streams and lakes with clear water. It typically lives in dark, muddy, or rocky crevices along the banks. It is usually found in forested regions at altitudes of , with most records between . There is an isolated population at an altitude of in Qinghai (Tibetan Plateau), but its taxonomic position is uncertain and the site likely does not support giant salamanders anymore due to pollution.